As a general rule, calories burned while running = 2/3 calorie x your weight x #miles.
For me, that's about 80 cals per mile. Or, for a 5 mile run, it's 400 cals. I think the composition of that is important, it needs to be carb rich before the run to give energy, and protein rich after the run to give my body building blocks to heal. I think they say a great after run recovery snack is carb:prot in 4:1 ratio, which is like a glass of chocolate milk.
You'd do well to also try to determine your calorie intake at which you neither gain or lose weight, that may help you figure out what your daily intake should be when you factor in the cals you are burning during your training.
When I started training for my first (and so far, only) marathon, I lost about 10 pounds until about halfway into the program. Then I found I really needed to increase my food intake so I had the energy to run those 15+ mile long runs. I actually had to eat an extra snack at night before bedtime.
I never did count calories but I understand your need to continue this early in the course of your life-changing body alteration! Way to go!
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